On 17 November 2017 at 20:46, Matt Turner <matts...@gmail.com> wrote: > On Fri, Nov 17, 2017 at 12:34 PM, Dylan Baker <dy...@pnwbakers.com> wrote: >> Quoting Emil Velikov (2017-11-17 03:11:50) >>> On 16 November 2017 at 22:21, Dylan Baker <dy...@pnwbakers.com> wrote: >>> > Quoting Emil Velikov (2017-11-16 03:35:17) >>> >> Hi Dylan, >>> >> >>> >> On 16 November 2017 at 01:10, Dylan Baker <dy...@pnwbakers.com> wrote: >>> >> > This patch checks for an and then enables sse4.1 optimizations if the >>> >> > host machine will be x86/x86_64. >>> >> > >>> >> Hell yeah, SSE is coming to town :-) >>> >> >>> >> Will this work if the user disables SSE4.1, say via CFLAGS=-mno-sse4.1 >>> >> meson ...? >>> >> My meson is still bit rough, so I could not quite grok ^^ by reading >>> >> through the patch. >>> >> >>> >> Thanks >>> >> Emil >>> > >>> > It'll explode horribly. Id didn't see any special handling of that in >>> > autotools >>> > build though either, did I miss something? >>> > >>> In autotools it's handled before the normal ld invocation. >>> >>> Namely: configure.ac does: >>> - construct a program using sse4.1 intrinsicts >>> Note: return _mm_...() is required otherwise the whole program will be >>> optimised away >>> - the -msse is passed first and then the user flags (-mno-sse and/or >>> anything else) >>> - the user -mno-sse takes precedence, hence the test program fails to build >>> - set see_supported=false and don't build the SSE optimised static library >>> >>> HTH >>> Emil >> >> That's an interesting question. So arguments passed via CFLAGS and friends >> will >> be passed to tests, but the arguments passed explicitly to those tests are >> appended, so -msse4.1 will take precedence. I'm also pretty sure there isn't >> a >> way to check the arguments passed via -Dc_args or CFLAGS (they're treated as >> default arguments, like the c_std in the project() argument). I asked on >> #mesonbuild, but I haven't gotten an answer yet (Fridays are pretty slow >> everywhere). >> >> I think currently the only way to control this would be to have a meson >> option >> to turn off optimizations, and I really don't like that. > > The original bug report of "Mesa doesn't build with -mno-sse4.1" was > in Gentoo's bugzilla; https://bugs.gentoo.org/503828 > > There's no compelling reason to support that configuration because > since the -msseX flags are off by default... in order for the > -mno-sseX flag to do anything the user must be enabling them somehow > (likely via -march=...). Using -march=... only to disable particular > instruction sets seems pretty idiotic. > I'm confused - it isn't the user but Mesa's build system which enables -msseX, right? Using -msseX is a good thing, but if the binary produced causes bugs the builder/user has no way to disable it.
Thanks Emil _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
